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The direct reduction process of coal-based composite pellet involves a series of physicochemical reactions. This paper reports a 3D unsteady mathematical model for simulation of heat transfer, mass...

We propose a novel polarization-maintaining supermode fiber containing quasi-elliptically arranged high-index cores. Numerical simulation indicates that such a fiber could support up to 20 distinct modes with different polarization states and spatial orientations. At 1550 nm, all the 20 modes are separated from their adjacent modes with effective refractive differences beyond 10- 4 . We also investigate the influence of parameters on mode number and effective area of the proposed fiber. Wavelength-dependent performance is analyzed subsequently ranging from 1500 to 1630 nm. The proposed fiber could guide 20 modes with low dispersion over the entire C-band. This letter illustrates that the proposed fiber might be a promising candidate for mode division multiplexing to enhance optical transmission capacity.

Under the condition of large water immersion, surface-piercing propellers are inclined to be heavy loaded. In order to improve the hydrodynamic performance of the surface-piercing propeller, the installation of a vent pipe in front of a propeller disc is more widely used in the propulsion device of high speed planning crafts. Based on computational fluid dynamics (CFD) method, this paper studied the influence of diverse vent pipe diameters on hydrodynamic performance of the surface-piercing propeller under full water immersion conditions. The numerical results show that, with the increase of vent pipe diameters, the thrust and torque of the surface-piercing propeller decrease after ventilation, and the efficiency of the propeller increases rapidly, the low pressure area near the back root of the blade becomes smaller and smaller gradually, and the peak of periodic vibration of thrust and torque can be effectively reduced. The numerical results demonstrate that the installation of artificial vent pipe effectively improves the hydrodynamic performance of surface piercing propeller in the field of high speed crafts, and the increase of artificial vent pipe diameter plays an active role in the propulsion efficiency of the surface-piercing propeller.

Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament (PDL) as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g (100 g=0.98 N) were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 kPa (capillary pressure) and 12.8 kPa (80% of human systolic blood pressure) was considered to be optimal, whereas an absolute strain exceeding 0.24% (80% of peak strain during canine maximal moving velocity) was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces (40-44 g for distal-direction and 28-32 g for labial-direction) were smaller than the translation forces (130-137 g for distal-direction and 110-124 g for labial-direction). In addition, the optimal forces for labial-direction motion (110-124 g for translation and 28-32 g for tipping) were smaller than those for distal-direction motion (130-137 g for translation and 40-44 g for tipping). Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.

The Central Line Workshop (CLW) was introduced at our institution to better train residents in safe placement of the central venous catheter (CVC). This study sought to determine if immediate performance improvements from the CLW are sustained 3 months after the training for residents with various levels of experience.Twenty-six emergency medicine residents completed the CLW, which includes online modules and experiential sessions in anatomy, ultrasound, sterile technique, and procedural task training. Demonstration of the synthesis of these skills including placement of both internal jugular and subclavian CVCs was assessed using a task trainer. Each resident was also tested approximately 3 months before and 3 months after the CLW. Residents were assessed using a validated CVC proficiency scale.Residents' CVC proficiency scores (percentage of items performed correctly during the assessment station) improved after CLW (0.6 vs. 0.93, P0.05). At 3 months after CLW testing, there was apparent skill decay from the CLW but overall improvement compared with baseline testing (0.6 vs. 0.8, P0.05). There was no significant difference in procedure time after CLW training. The postgraduate year 1 group showed the greatest improvement of CVC skill after CLW training.Resident CVC placement performance improved immediately after the CLW. Although performance 3 months after the CLW revealed evidence of skill decay, it was improved when compared with initial baseline assessment. Novice learners had the greatest benefit from the CLW.

Development of bottom water reservoir with horizontal well can effectively slow down water coning and avoid early water breakthrough in oil wells, which promotes the extensive application of horizontal well in bottom water reservoir. In this paper, literatures about horizontal well are investigated, and the latest research trend is summarized. All factors such as reservoirs, fluid property and production mode to influence horizontal well performance in bottom water reservoir are systematically studied by using reservoir numerical simulation. Based on the calculation results of reservoir parameters of the pilot area, comprehensive analysis to the key factors which affecting horizontal well performance is carried out and the influence degree of various factors on oil recovery is obtained. In a word, the research results in this paper can provide criteria for the design or optimization of horizontal well development in bottom water reservoir.

Performing the 3-D numerical modeling of the automobile covering parts by the Pro/E software, creating both addendum and blank holding surfaces, and importing them into the DYNAFORM so that a FEM model can be created. Use the DYNAFORM to perform the simulation calculation and analysis, and study the influences of the factors such as friction coefficient, die clearance and material parameters (n and r values) on the stamping formability. The results show that the parameters such as friction coefficient between die and blank, die clearance and the v value in the material parameters play the key role in the the blank flowability, and have the significant influence on the stamping result.

In this paper, the distribution and variation trend of temperature and velocity fields were obtained by numerical simulation of the casting process of shell die casting. According to the results of the numerical simulation, the die casting technology was optimized. The sound castings were produced. It was verified that shrinkage cavity and porosity could be reduced by increasing injected pressure and decreasing pouring and mould temperatures. The reliability of numerical simulation of die casting process was proved. In addition, the qualified products were obtained on the basis of the optimized die-casting parameters from the simulation results.

In the milling process of thin wall workpiece, the more cutter flutes, the high metal remove ratio can be gotten. Milling forces with two-futes and four-flutes milling cutter were anlysised and compared using finite element method. The possibility and advantage of machining thin wall workpiece with four flutes milling cutter was introduced. The four flutes cutter can improve the metal remove ratio, and cutting force is more uniform in general.

The new Accreditation Council for Graduate Medical Education (ACGME) duty-hour standards for residents and fellows went into effect in 2011. These regulations were designed to reduce fatigue-related medical errors and improve patient safety. The new shift restrictions, however, have led to more frequent transitions in patient care (handoffs), resulting in greater opportunity for communication breakdowns between caregivers, which correlate with medical errors and adverse events. Recent research has focused on improving the quality of these transitions through standardization of the handoff protocols; however, no attention has been given to reducing the number of transitions in patient care. This research leverages integer programming methods to design a work shift schedule for trainees that minimizes patient handoffs while complying with all ACGME duty-hour standards, providing required coverage, and maintaining physician quality of life. In a case study of redesigning the trainees’ schedule for a Mayo Clinic Medical Intensive Care Unit (MICU), we show that the number of patient handoffs can be reduced by 23 % and still meet all required and most desired scheduling constraints. Furthermore, a 48 % reduction in handoffs could be achieved if only the minimum required rules are satisfied.

Based on Lyapunov theory, the adaptive generalized synchronization between Chen system and a multi-scroll chaotic system is investigated. According to the form of target function a proper adaptive controller is designed, by which the controlled Chen system can be synchronized with a multi-scroll chaotic system including unknown parameters. The Lyapunov direct method is exploited to prove that the synchronization error and parameter identification error both converge to zero. Numerical simulation results verify the feasibility of the proposed method further.